1. Field of the Invention
This technology relates to linearized power amplifiers (LPAs).
2. Description of Related Art
Prior LPAs have a variety of issues as follows.
1. Prior LPA Efficiency and Linearity Issues:
Prior linearized power amplifiers have several deficiencies including less than optimal efficiency, linearity, and performance over a voltage range and over a temperature range. One of the primary goals of any LPA is to provide a linear signal at as high a power level as possible. In a prior art LPA, the LPA current increases steadily with RF power out. At some high RF power level, clipping begins to occur to the RF signal thereby degrading linearity and efficiency at high RF power. One approach is to delay the onset of clipping, by reducing the bias current at high RF power levels to delay the onset of clipping.
2. Prior LPA Performance Over Voltage Range Issue:
Prior LPAs also tend to have significant variation in performance as power supply voltage level varies.
3. Prior LPA Performance Over Temperature Range Issue:
Another shortcoming of prior LPAs is LPA performance over a temperature range. A prior art LPA with a fixed bias exhibits large changes in current/efficiency and linearity performance as the temperature changes from cold to room to hot.
4. Other prior LPA Issues:
Some prior art LPAs attempt to improve these deficiencies by utilizing complex digitally modulated PA and digital pre-distortion schemes. However these types of designs are complex to design and implement, and tend to be large and consume much power. They are also usually silicon based technologies with inherently inferior RF characteristics, they cannot take advantage of the inherently superior RF characteristics of GaAs materials. Our novel LPA would be relatively simple and compact and able to be implemented on GaAs as a single die.